Vibration sensors can be useful for monitoring the condition of rotating machinery, where overheating or excessive vibration could indicate excessive loading, inadequate lubrication, or bearing wear. Commercial vibration sensors use a piezoelectric ceramic strain transducer attached to a metallic proof mass in order to respond to an externally imposed acceleration.
It is also possible to use a MEMS accelerometer with a capacitive output such as the one made by Analog Devices. These devices provide an acceleration output directly and do not require FM demodulation.
However, alternative means for measuring vibration, which would have decreased cost, easier manufacturing techniques, more reliability and additional features, are always desired. It would be important to develop new sensors which would overcome some of the shortcomings of current sensors, particularly by offering the many advantages of fiber optic interconnections. Of particular interest are sensors which have immunity from EMI, are intrinsically safe, and permit operation at much higher temperatures than the prior art.
Also, since vibration is often measured or monitored to determine or anticipate defects and/or machine wear, it would be desirable to measure the temperature of the object being monitored since an increase in heat often indicates increased friction or stress that may in time lead to failure of the object.
Accordingly, it would be of great advantage in the art if an improved vibration sensor could be provided.
It would be another great advance in the art if the vibration sensor would also permit measurement of other physical properties such as the temperature of the vibrating element.
Other advantages will appear hereinafter.